CN110980883A - Method for removing divalent ions in water by whole membrane method - Google Patents
Method for removing divalent ions in water by whole membrane method Download PDFInfo
- Publication number
- CN110980883A CN110980883A CN201911342822.7A CN201911342822A CN110980883A CN 110980883 A CN110980883 A CN 110980883A CN 201911342822 A CN201911342822 A CN 201911342822A CN 110980883 A CN110980883 A CN 110980883A
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- Prior art keywords
- water
- nanofiltration membrane
- divalent
- membrane system
- ions
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/02—Temperature
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/03—Pressure
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/06—Controlling or monitoring parameters in water treatment pH
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
Abstract
The invention discloses a full-membrane method for removing divalent ions in water. The method firstly enters a nanofiltration membrane system with negative charge to remove divalent anions, and part of divalent cations are removed simultaneously; the water produced by the system enters a positively charged nanofiltration membrane system to remove residual divalent cations, the produced water does not contain divalent ions, and the operating process parameters of the negatively charged nanofiltration membrane system and the positively charged nanofiltration membrane system are set as follows: the recovery rate should be controlled between 50% and 60%, and the operating pressure should be controlled between 0.3 MPa and 0.7 MPa. The method can selectively remove divalent cations and divalent anions, reduce energy consumption and reduce operation cost.
Description
Technical Field
The invention relates to the field of industrial sewage treatment, in particular to a method for removing divalent ions in water by a full-membrane method.
Background
Water typically contains a large amount of divalent ions, particularly industrial wastewater, and divalent ions in water typically include anions (e.g., sulfate, carbonate, sulfite, hydrogen phosphate, etc.) and cations (e.g., calcium, magnesium, copper, etc.). At present, the method capable of removing two types of divalent ions simultaneously is mainly a reverse osmosis technology, but a reverse osmosis membrane material can remove most of monovalent ions while removing the divalent ions, so that the treatment cost is high due to no selectivity.
For divalent cations in water, especially for hardness (calcium, magnesium ions), precipitation or ion exchange resins are currently used in the industry for removal. The precipitation method comprises adding alkaline agent such as quicklime and sodium hydroxide to precipitate calcium magnesium ions and sulfate ions, flocculating the precipitate, and filtering to remove divalent ions. The method needs to add chemicals with the same molar weight as ions, has higher cost, large occupied area and longer time consumption in the process of precipitation and flocculation, and is very difficult to filter because the precipitated particles formed by magnesium ions are finer. The ion exchange method is to convert cations (mainly calcium and magnesium) in water into sodium ions by adopting ion exchange resin, thereby achieving the purpose of removing divalent cations. The essence of the method is that divalent cations are converted into monovalent cations, and the number of the ions does not decrease or increase reversely. Moreover, the ion exchange resin needs to be frequently increased, and the generated strong acid/strong base waste liquid also needs to be harmlessly treated at higher cost.
The reverse osmosis technology has high operation cost due to no selectivity. The precipitation method adopts a large amount of medicament for treatment, the cost is also higher, and a large amount of waste liquid which is difficult to treat, such as strong acid/strong base and the like is generated, so that extra treatment cost is generated; the method is effective to divalent cations, divalent anions, particularly sulfate ions, cannot be completely removed, and other methods are needed to be matched if the requirement on the quality of produced water is high. The ion exchange method only exchanges divalent cations into monovalent cations, does not really reduce the content of impurity ions, and the ion exchange resin needs to be regenerated frequently to generate waste liquid which is difficult to treat, such as strong acid/strong base and the like.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provide a full-membrane method for removing divalent ions in water.
The invention relates to a full-membrane method for removing divalent ions in water, which is realized by the following technical scheme that firstly, the water enters a negative-charged nanofiltration membrane system to remove divalent anions, and part of divalent cations are removed simultaneously; the water produced by the system enters a positively charged nanofiltration membrane system to remove residual divalent cations, the produced water does not contain divalent ions, and the operating process parameters of the negatively charged nanofiltration membrane system and the positively charged nanofiltration membrane system are set as follows: the recovery rate should be controlled between 50% and 60%, and the operating pressure should be controlled between 0.3 MPa and 0.7 MPa.
The cleaning cycle of the negative charge nanofiltration membrane system and the positive charge nanofiltration membrane system is about 1-2 months, or the daily water yield is reduced by 5% -10%.
The negative charge nanofiltration membrane system needs to be arranged in front of the positive charge nanofiltration membrane system, so that the pollution rate of the positive charge nanofiltration membrane can be greatly reduced, the backwashing period is prolonged, and the service life of the positive charge nanofiltration membrane is prolonged.
Compared with a nanofiltration membrane charged with negative electricity, the nanofiltration membrane charged with positive electricity is easily polluted by colloid in water (generally charged with negative electricity). Therefore, besides the protection of the pre-loaded nanofiltration membrane, the recovery rate is properly controlled, the operation pressure is reduced, and the cleaning period is shortened.
The process can adopt a rolled nanofiltration membrane, a hollow fiber nanofiltration membrane and a combination thereof. If the hollow fiber nanofiltration membrane is adopted, an unsteady state operation process can be combined, and a backwashing mode can be adopted in the corresponding cleaning process. The combination of the two can greatly improve the pollution resistance of the film, and is particularly suitable for the environment with poor water quality.
For water with high calcium ion, additives such as scale inhibitor and the like can be properly added to prevent scaling. For the hollow fiber nanofiltration membrane, chemical substances such as citric acid and the like can be added in the backwashing process to enhance the cleaning effect.
The process can receive MBR produced water in wastewater treatment, or receive secondary sedimentation tank/ultrafiltration effluent in feed water, and can realize the functions of removing divalent ions, denitration, hardness removal and the like.
Compared with the prior art, the invention has the beneficial effects that:
1. the method can selectively remove divalent cations and divalent anions, reduce energy consumption and reduce operation cost.
2. The method can be operated continuously, is simple and convenient to operate, and does not need to be regenerated periodically.
3. The method of the invention does not use strong acid/strong base and other chemical agents.
4. The method of the invention has no waste liquid, has little pollution to the environment and is a more environment-friendly treatment method.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Comparative example 1
20000-shaped charge-water 26000 tons of sewage are treated every day in a sewage treatment enterprise in a chemical industrial park, and the produced water of a Membrane Bioreactor (MBR) mainly comprises 35-50 mg/L of calcium ions, 25-40 mg/L of magnesium ions, 300 mg/L of sulfate ions and 1-3NTU of turbidity. The enterprises precipitate calcium and magnesium ions by adding sodium hydroxide. After precipitation and flocculation, the product is neutralized to be neutral, and is subjected to denitration by a rolled nanofiltration membrane for recycling of part of enterprises.
Comparative example 2
The MBR produced water of the enterprise is firstly subjected to denitration by a rolled nanofiltration membrane, and then the hardness of the MBR produced water is removed by adopting ion exchange resin, so that the produced water is recycled by part of enterprises.
Comparative example 3
The MBR produced water firstly passes through the ultrafiltration membrane, and the produced water enters a reverse osmosis system to remove divalent ions and part of monovalent ions for recycling of part of enterprises.
Comparative example 4
The MBR produced water of the enterprise is firstly treated by a positively charged spiral-wound nanofiltration membrane and then enters a negatively charged spiral-wound nanofiltration membrane system, and the produced water is recycled by part of enterprises.
Example 1
The MBR produced water of the enterprise is firstly treated by a negatively charged spiral-wound nanofiltration membrane and then enters a positively charged spiral-wound nanofiltration membrane system, and the operating technological parameters of the negatively charged nanofiltration membrane system and the positively charged nanofiltration membrane system are set as follows: the pressure is 0.7MPa, the recovery rates are 75% and 67%, the temperature is 35 ℃, the pH =7.3, and the produced water is recycled.
Example 2
MBR produced water is firstly treated by a negatively charged hollow fiber nanofiltration membrane and then enters a positively charged hollow fiber nanofiltration membrane system, and the rest is the same as that in the embodiment 1.
Example 3
MBR produced water is firstly treated by a negatively charged roll-type nanofiltration membrane and then enters a positively charged hollow fiber nanofiltration membrane system, and the rest is the same as that in the embodiment 1.
Example 4
MBR produced water is firstly treated by a negatively charged hollow fiber nanofiltration membrane and then enters a positively charged roll type nanofiltration membrane system, and the rest is the same as that in the embodiment 1.
Example 5
The quality of MBR produced water is deteriorated, the calcium ion concentration is 130-150 mg/L, the magnesium ion concentration is 60-75 mg/L, the sulfate ion concentration is 370-450mg/L, and the turbidity is 2-7 NTU. The rest is the same as in example 1.
Example 6
The quality of MBR produced water is deteriorated, the calcium ion concentration is 130-150 mg/L, the magnesium ion concentration is 60-75 mg/L, the sulfate ion concentration is 370-450mg/L, and the turbidity is 2-7 NTU. The rest is the same as in example 2.
Example 7
The quality of MBR produced water is deteriorated, the calcium ion concentration is 130-150 mg/L, the magnesium ion concentration is 60-75 mg/L, the sulfate ion concentration is 370-450mg/L, and the turbidity is 2-7 NTU. The rest is the same as in example 3.
| Floor area, square meter | Cost per ton of water, yuan/ton | Cleaning/regeneration cycle, week | |
| Comparative example 1 | 3200 | 2.2 | 3-5 |
| Comparative example 2 | 800 | 1.9 | 1-2 |
| Comparative example 3 | 750 | 2.1 | 8-12 |
| Comparative example 4 | 720 | 3 | 2-3 |
| Example 1 | 720 | 1.5 | 12-16 |
| Example 2 | 720 | 1.5 | 24-50 |
| Example 3 | 720 | 1.5 | 16-20 |
| Example 4 | 720 | 1.5 | 12-16 |
| Example 5 | 720 | 1.8 | 8-10 |
| Example 6 | 720 | 1.8 | 24-30 |
| Example 7 | 720 | 1.8 | 12-16 |
From the above table, it can be seen that the use of the full membrane process to remove divalent ions can simultaneously achieve a smaller footprint, lower water cost per ton and longer cleaning cycle. In particular, the hollow fiber nanofiltration membrane has more outstanding pollution resistance than a roll type membrane, and is particularly suitable for the environment with worse water quality.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (2)
1. A full-membrane method for removing divalent ions in water is characterized in that firstly, the water enters a negatively charged nanofiltration membrane system to remove divalent anions, and part of divalent cations are removed at the same time; the water produced by the system enters a positively charged nanofiltration membrane system to remove residual divalent cations, the produced water does not contain divalent ions, and the operating process parameters of the negatively charged nanofiltration membrane system and the positively charged nanofiltration membrane system are set as follows: the recovery rate should be controlled between 50% and 60%, and the operating pressure should be controlled between 0.3 MPa and 0.7 MPa.
2. The method for removing divalent ions in water by using the full membrane method as claimed in claim 1, wherein the washing period of the negatively charged nanofiltration membrane system and the positively charged nanofiltration membrane system is 1-2 months, or the water yield per day is reduced by 5% -10%.
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| CN201911342822.7A CN110980883A (en) | 2019-12-24 | 2019-12-24 | Method for removing divalent ions in water by whole membrane method |
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| CN201911342822.7A CN110980883A (en) | 2019-12-24 | 2019-12-24 | Method for removing divalent ions in water by whole membrane method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112079466A (en) * | 2020-09-16 | 2020-12-15 | 烟台金正环保科技有限公司 | Full-membrane seawater desalination treatment system and method |
| CN114249385A (en) * | 2021-12-02 | 2022-03-29 | 中煤科工集团西安研究院有限公司 | Water treatment process and index obtaining method of positive/negative charge nanofiltration device |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112079466A (en) * | 2020-09-16 | 2020-12-15 | 烟台金正环保科技有限公司 | Full-membrane seawater desalination treatment system and method |
| CN112079466B (en) * | 2020-09-16 | 2022-08-09 | 烟台金正环保科技有限公司 | Full-membrane seawater desalination treatment system and method |
| CN114249385A (en) * | 2021-12-02 | 2022-03-29 | 中煤科工集团西安研究院有限公司 | Water treatment process and index obtaining method of positive/negative charge nanofiltration device |
| CN114249385B (en) * | 2021-12-02 | 2023-08-15 | 中煤科工集团西安研究院有限公司 | Water treatment process and index obtaining method of charged positive/negative electric nanofiltration device |
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